If you do so, prepare to waste countless hours on debugging seriously weird and peculiar bugs, which may only manifest itself after some time.
Never ever update only glibc. If you do, update the rest of the system too. And for good measure, reboot. All important jobs are started with cron, right?
This time it was Boost ASIO 1.50. Opening TCP servers was just not possible. The same program, only using Boost 1.42 worked like a charm. And finally, the Boost 1.50 version of the program ran fine on an other computer. About the day wasted. Solution? Downgrade glibc.